The disclosure relates to a laminate and a thermoelectric conversion element provided with a layer having a predetermined crystal structure on the laminate. Priority is claimed on Japanese Patent Application No. 2017-068914, filed Mar. 30, 2017, the content of which is incorporated herein by reference.
In recent years, various thermoelectric conversion elements utilizing the thermoelectric properties of materials have been examined. Examples thereof include power generation elements utilizing the Seebeck effect caused by a temperature difference between the outside air and a human body, and power generation elements utilizing waste heat from an automobile, an incinerator, a heater, or the like. Bi2Te3 is a material that is currently put to practical use as a thermoelectric conversion material. This material has high conversion efficiency. However, since both Bi and Te as the constituent elements are expensive and Te is toxic, it is difficult to achieve mass production, a reduction in costs, and a reduction in environmental burdens. Therefore, there is a demand for a highly efficient thermoelectric conversion material replacing Bi2Te3.
As candidates for non-toxic and inexpensive thermoelectric conversion materials, Heusler alloys such as Fe2VAl have attracted attention. There has been consideration of techniques for thin film crystallization to further improve the thermoelectric properties of such Heusler alloys (PCT International Publication No. WO2016/129082 and Japanese Unexamined Patent Application, First Publication No. 2013-21089). Thin film crystallization has attracted attention as a technique for improving element properties not only in the technical field of thermoelectric conversion but also in the technical fields related to high-temperature superconductivity, oxide electronics for ferroelectric materials or the like, and spintronics for magnetic materials or the like.
In a case where a Heusler alloy such as Fe2VAl is subjected to thin film crystallization for the purpose of improving the properties of a thermoelectric conversion element, it is preferable to use a MgO substrate as an underlying substrate from the viewpoint of controlling the crystal orientation. Furthermore, even when a thin film of a high-temperature superconductor, a ferroelectric material related to oxide electronics, or a magnetic material related to spintronics is formed, it is preferable to use a MgO substrate as an underlying substrate. However, since the MgO substrate is expensive, it is difficult to put a thermoelectric conversion element, a high-temperature superconductor, a magnetic material, and the like utilizing the MgO substrate as a substrate to practical use as products.